Former Chief Whip Andrew Mitchell admitted swearing but always denied using the word "pleb" during the altercation with police in Downing Street on 19 September 2012. Why was this old-fashioned term, and not the undisputed obscenity, seen as the most damaging part of the allegations?

'The masses'

A look back at the word's origins show why it could be, in the words of Mr Mitchell's lawyer, so "toxic" in the context it was allegedly used.

It comes from Roman times, when plebeians were any tribe without advisers to the King. In time, the word - which is related to the Greek word for crowd, plethos - came to mean the common people.

It had a pejorative use back then, said Edith Hall, professor of classics at King's College London.

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The word 'pleb' can be traced back to Roman times, but its use has died down in recent years

In 2012, after the Downing Street row emerged, she told BBC Radio 4 the word was "almost always used by the ruling classes who were the people that got to write things, say things and decide things about the great masses".

This theme was continued in the English public schools of the 18th and 19th Centuries, Ian Brookes, consultant editor at Collins Language, said.

He said: "In public school parlance, a pleb was a pupil who was not a member of the landed classes."

Dictionary corner

Although its use has died down in recent years, the connotations attached to the word remain, and Mr Mitchell - said to have earned the nickname Thrasher at Rugby public school - was at pains to distance himself from the Sun's report.

While he apologised to David Cameron for swearing at the officer, during the libel trial his counsel said he would never such a "toxic and class-laden expression" to put someone down because of their class, background or job.

In a character witness statement supporting Mr Mitchell, newspaper columnist Matthew d'Ancona said class had been an issue for the coalition government, which had been criticised for the number of private school and Oxbridge-educated people it contained.

Writing in the Telegraph in the aftermath of the row in 2012, Mr d'Ancona said: "For a senior minister to call the people protecting him and his colleagues 'plebs' would be no small matter.

"It would confirm every ghastly suspicion that the Tory party is led by people who really do believe themselves born to rule and therefore regard the police as no more than proletarian shock-troops at their beck and call.